In the area of friction and seal components for demanding applications, seal designs are often compromised by the need to choose among materials which have exclusive and independent benefits, and sometimes conflicting characteristics. The seal designs are often compromised in material selection because, while some materials have beneficial properties in certain respects, the materials may have disadvantages, or less desirable characteristics, in other respects. For example, some seal materials (i.e. carbon/graphites) have self-lubricating properties, and therefore perform very well in dry run and process upset conditions. Typically, such materials also have a low modulus of elasticity, which allows the materials to deflect against the mating face of a seal (which is usually a high modulus ceramic). However, because of the low modulus, such materials lack strength and stiffness. Further, the materials also lack high oxidation resistance.
Other seal materials (e.g. self-sintered silicon carbides) have superior strength and a high modulus of elasticity, which provides the stiffness necessary to give the entire seal assembly stability and strength, and have high oxidation resistance. However, such materials are not self-lubricating. Therefore, the materials have poor dry running and/or process upset response characteristics.